Conventionally, a vehicular hydraulic control device is known which includes a first oil pump and a second oil pump, wherein the first oil pump is configured to be driven by a vehicle drive source, and the second oil pump is configured to be driven by an electric motor, and wherein the vehicular hydraulic control device is configured to control the first and second oil pumps based on a driver-requested driving force, in a manner to ensure a hydraulic pressure required to prevent slipping of a power transmission part such as a clutch or a variator which is disposed between the vehicle drive source and a driving wheel for transmitting power (see a patent document 1, for example).
However, during start or acceleration in a low vehicle speed region in which a rotational speed of the vehicle drive source is low, a rotational speed of the first oil pump is also low, and it may be impossible to ensure a sufficient hydraulic pressure with respect to the required hydraulic pressure only by a discharge pressure of the first oil pump. In such a situation, it is conceivable to compensate for a shortage of the discharge pressure of the first oil pump by a discharge pressure of the second oil pump. However, in the conventional vehicular hydraulic control device where the discharge pressure of the second oil pump is set to the hydraulic pressure of the shortage (quantity of compensation), it is possible that an actual hydraulic pressure based on the discharge pressures of the first and second oil pumps becomes lower than the required hydraulic pressure, due to leaking or variation in hydraulic pressure. Since the rotational speed of the vehicle drive source is low and the discharge pressure of the first oil pump is likely to vary especially in a low vehicle speed region such as in a state of vehicle start, it is possible that the discharge pressure of the first oil pump becomes lower than assumed, and the required hydraulic pressure cannot be obtained. If the required hydraulic pressure cannot be obtained, a slip may occur in the power transmission part, so that it is impossible to transmit a driver-intended driving force to driving wheels.
The present invention is targeted for providing a vehicular hydraulic control device capable of ensuring a required hydraulic pressure in response to an occurrence of a requested driving force in a low vehicle speed region in which an output of a first oil pump is unstable.